The existence of infectious diseases such as AIDS and hepatitis has highlighted the danger to which medical personnel may be exposed when treating patients by means of catheter devices where a sharp needle tip is used to pierce the skin of a patient. Medical personnel have been infected by physical contact with, or accidental prick by an infected needle (needle-stick).
In order to protect medical personnel against inadvertent needle-stick, a number of solutions have been developed whereby a protective means incorporated within the catheter prevents physical contact with the needle after use and hence against inadvertent needle-stick.
One known device for protecting the needle ,both before and after use, is described in European Patent Publication Number 0599564 in which a needle is arranged within a housing and is displaceable between a first retracted position and a second extended position. Means is provided for displacing the needle between said first and second positions. A sealing means for sealing the initially open distal end of the housing, is connected to the displacing means, at least initially. The sealing means during displacement of the needle from said first retracted position to said second position, is moved in the direction towards the open distal end of the housing to a sealing position and is then fixed in said sealing position, substantially sealing the interior of the housing.
The structure described in European Patent Publication Number 0599564, although effective to prevent inadvertent needle-stick, is complicated and relatively expensive to manufacture. Furthermore, the structure does not give any clear visible sign to show the user that the needle is locked in the protected position.
Another known device for protecting against inadvertent needle-stick is described in U.S. Pat. No. 5,447,501. In this document, there is described an infusion catheter assembly including a hollow needle having a sharpened distal tip for piercing the skin of a patient. The needle is mounted on a hub forming part of a casing. A needle protection device is attached to the hub and includes a rigid front end and a rear flexible end. The rigid front end incorporates a resilient member which, in a needle protected position of the needle, prevents movement of the needle in a longitudinal sense. Furthermore, the rigid front end also includes a forwardly extending boss for supporting a cannula hub forming part of a cannula assembly.
This device is a relatively simple and economic device and is effective to minimize the danger of inadvertent needle stick.
However, there is a risk that the user could attempt to disengage the cannula hub from the rigid front end before the needle is completely withdrawn inside the protection device and locked therein.
It is an aim of the present invention to provide a simple but effective means for protecting the point of a needle forming part of a medical device, such as an intravenous catheter assembly, and to provide means which prevents the user from disengaging a cannula hub from the catheter assembly before the needle is completely withdrawn inside a protective housing.